BERLIN (Reuters) - Several German lawmakers said on Sunday the country's soldiers working at Turkey's Incirlik airbase should be brought home if Ankara continued to prevent parliamentarians from visiting the station.

Turkey, angered by a resolution passed by the German parliament last month that branded the 1915 massacre of Armenians by Ottoman forces a genocide, has denied German lawmakers access to the base.

Chancellor Angela Merkel said the parliamentarians must be allowed to visit the 250 soldiers at the base who are taking part in NATO operations against Islamic State militants in Iraq but she stopped short of threatening to withdraw the soldiers.

Relations between Germany and Turkey, crucial partners in the effort to stem mass migration to Europe, have been strained in recent months. President Tayyip Erdogan was angered by the broadcast of a satirical song about him on German television and in April launched legal action against the comedian who wrote it. The Armenian resolution last month, which prompted Ankara to recall its ambassador, compounded the rift.

A leader of Germany's opposition Greens, Cem Ozdemir, who is of ethnic Turkish origin, told ARD television the situation was unacceptable.

"As lawmakers who send soldiers to places, we must know where they are, how they are and be able to talk to the soldiers. If that is not possible in Turkey then the soldiers must come back to Germany," he said.

Lawmakers approve military spending and investment in infrastructure at the base.

Asked if she would consider withdrawing troops from Incirlik if no agreement were reached, Merkel said she was focusing on resolving the matter by talking.

"A way must be found for the lawmakers to visit the soldiers. We must continue to work on this, the solution is not yet there," she told broadcaster ZDF in an interview.

Merkel met Turkish President Tayyip Erdogan on the sidelines of a NATO summit in Warsaw on Saturday. She said the atmosphere was constructive but the differences remained.

Andreas Scheuer, General Secretary of the Bavarian Christian Social Union (CSU) who are part of Merkel's conservative bloc in parliament, said lawmakers had to be allowed to visit soldiers.

"As a result of his behaviour, Turkish President Erdogan is risking the withdrawal of the German army," he told Monday's Tagesspiegel daily, according to extracts sent in advance.

Turkey accepts that many Christian Armenians living in the Ottoman Empire were killed in clashes with Ottoman forces during World War One but it denies that up to 1.5 million were killed and that the killings constitute a genocide. It also says many Muslim Turks died in the clashes.

(Reporting by Madeline Chambers; Editing by Gareth Jones and Raissa Kasolowsky)